CVE-2025-39737

Local denial of service via unyielding cleanup loop

Published Sep 11, 2025 · Updated May 12, 2026

Denial of service in Linux kmemleak on Linux and SIMATIC CN 4100 allows local users to cause a soft lockup during cleanup. The __kmemleak_do_cleanup() workqueue deletes tens of thousands of tracked objects in one loop, repeatedly taking a raw spinlock without yielding. Triggering requires a debug kernel with kmemleak enabled, pool exhaustion, many tracked objects, and concurrent memory hot-unplug activity.

CVSS severity5.5
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kmemleak on Linux and SIMATIC CN 4100 allows local users to cause a soft lockup during cleanup. The __kmemleak_do_cleanup() workqueue deletes tens of thousands of tracked objects in one loop, repeatedly taking a raw spinlock without yielding. Triggering requires a debug kernel with kmemleak enabled, pool exhaustion, many tracked objects, and concurrent memory hot-unplug activity.

The record

CVE
CVE-2025-39737
Published
Sep 11, 2025
Updated
May 12, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-20, CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. May 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <1ef72a7fedc5bca70e8cc980985790de10d407aa
  2. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <8d2d22a55ffe35c38e69795468a7addd1a80e9ce
  3. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <926092268efdf1ed7b55cf486356c74a9e7710d1
  4. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <9b80430c194e4a114dc663c1025d56b4f3d0153d
  5. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <9f1f4e95031f84867c5821540466d62f88dab8ca
  6. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <a04de4c40aab9b338dfa989cf4aec70fd187eeb2
  7. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <d1534ae23c2b6be350c8ab060803fbf6e9682adc
  8. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <e21a3ddd58733ce31afcb1e5dc3cb80a4b5bc29b
  9. Affected versionversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <f014c10d190b92aad366e56b445daffcd1c075e4
  10. Affected versionversion=5.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <1ef72a7fedc5bca70e8cc980985790de10d407aa; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <8d2d22a55ffe35c38e69795468a7addd1a80e9ce; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <926092268efdf1ed7b55cf486356c74a9e7710d1; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <9b80430c194e4a114dc663c1025d56b4f3d0153d; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <9f1f4e95031f84867c5821540466d62f88dab8ca; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <a04de4c40aab9b338dfa989cf4aec70fd187eeb2; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <d1534ae23c2b6be350c8ab060803fbf6e9682adc; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <e21a3ddd58733ce31afcb1e5dc3cb80a4b5bc29b; version=2abd839aa7e615f2bbc50c8ba7deb9e40d186768 <f014c10d190b92aad366e56b445daffcd1c075e4; version=5.4
Siemens · SIMATIC CN 4100version=0 <V5.0

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-401Missing Release of Memory after Effective Lifetime
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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